layout.scss

// ----------------------------------------------
// I want to define the important layout settings

// $columns: <integer> | <list>;
$columns: 12;

// $gutters: <ratio>;
$gutters: .25;

// $column-width: auto | <length>;
$column-width: auto;

// $container: auto | <length>;
$container: auto;

// -----------------------------------------------------
// I want to store an entire layout in a single variable
//
// - [container], columns, spacing
// - container is an (optional) length
// - columns can be an integer or list
// - spacing defines column-to-gutter size as two lengths, or single float ratio
//   (these can be used to set $column-width and $gutters)

$symmetrical: 4 .25;
$symmetrical-specific: 960px 12 (60px 20px);
$symmetrical-extended: (1 1 1 1) .25;

$asymmetrical: (1 3 5 2 1) .25;
$asymmetrical-specific: 80% (1 3 5 2 1) (3em 1em);

// --------------------------------------------------
// I want to override all the global settings at once

$any-layout: 660px 12 (60px 20px);

@include set-layout($any-layout);

// ------------------------------------------
// I want to use explicit breakpoint handling
//
// - set a breakpoint (using breakpoint plugin)
// - set a layout

$breakpoint: 50em;
$large: 12 .25;

@include breakpoint($break) {
  @include layout($large) {
    /* do what I want */
  }
}

// ---------------------------------------
// I to return the width of a column-group
//
// - columns
// - [optional] context
// - [optional] location

$width: span(3);
$nested: span(3 of 6);
$asymmetric: span(3 at 3 of (1 3 5 4 2));
$shortcut: span(last 3 of (1 3 5 4 2));

// ---------------------------------------------
// I want to return the width of a single gutter
//
// - [optional] context

$gutter: gutter();
$gutter: gutter(6);
$gutter: gutter(1 3 5 6 4 2);

static wouldn't be on the same level as float/isolate/flexbox of course - that would be a different thing, but still an output-related setting.

Now that I think about it, I wonder what flexbox grids actually would look like. I don't really know. Has anyone done a lot of work on that?